The present invention relates generally to methods and systems for coating a substrate. More particularly, the present invention relates to methods and devices for depositing a metal layer onto a thermoform that is of a sufficient thickness for shielding of electromagnetic interference (xe2x80x9cEMIxe2x80x9d) and radiofequency interference (xe2x80x9cRFIxe2x80x9d).
U.S. Pat. No. 5,811,050 to Gabower, which is incorporated herein by reference, has proposed depositing a thin layer of metal onto a thermoform to create a protective barrier for EMI and RFI. One method for depositing the metal layer onto the thermoform is a batch mode process. A first step of the method includes thermoforming (i.e. shaping) the thermoform substrate. The shaped thermoforms are then placed into the vacuum chamber and a vacuum source is used to create a vacuum in the chamber. A source of metal is vaporized and deposited onto the thermoform substrate.
Unfortunately, the batch processes is slow, time consuming, and impurities can be introduced into the metallized object during transport into and out of the vacuum chamber. For example, one specific problem with the batch process is the creation of the vacuum environment in the deposition chamber. Because the vacuum chamber usually has a large volume (typically about 300,000 in3), the creation of the vacuum environment takes a long period of time to create. Another problem of batch processing is that the thermoform must be separately shaped and cut from the thermoform sheet and it is often necessary to manually handle the thermoformed substrate, both prior and subsequent to the coating process. Care must be taken in such handling steps to avoid contamination or introduction of impurities which may lead to imperfections in the metal layer and leakage in the EMI/RFI shield.
Therefore, what is needed are vapor deposition processes and apparatuses for coating objects with a coating material that have improved process speed and improved process control characteristics.
U.S. Pat. No. 5,908,506 provides a continuous vapor deposition apparatus that appears to have stationary process chambers. U.S. Pat. No. 5,811,050 describes an apparatus for vacuum depositing a metallic coating on thermoformed blanks that are placed on a carrier that revolves around a stationary tungsten filament. U.S. Pat. No. 5,076,203 recites passing a web over spools past a stationary source of metal and an electron beam heater. U.S. Pat. No. 4,261,808 describes a vertical vacuum coating apparatus that deposits a metal layer onto a moving substrate with a fixed cathode system.
The present invention provides improved methods and systems for depositing a coating material onto a substrate. In exemplary embodiments, the methods and systems are used for vacuum metallizing a thermoform or other substrate for creating an EMI/RFI shield.
The systems of the present invention generally have at least one processing apparatus that is movable orthogonal to a plane of the substrate. The processing apparatus can be moved adjacent the substrate or to contact the substrate, a platform, and/or a second processing apparatus to process the substrate. In some embodiments, the processing apparatuses have a small volume cavity in which a vacuum can be created for the delivery of a vaporized metal or other coating material. The small vacuum cavities of the processing apparatuses of the present invention allow a vacuum source to create a vacuum environment in a shorter amount of time than conventional vacuum chambers, thus improving the speed of manufacturing of the substrates. The cavities of the processing apparatuses can house a shaping assembly, a pre-treatment assembly (e.g. glow discharge), a metallizing assembly (e.g. vacuum metallization, arc plasma deposition, ion deposition), heating elements, a cutting assembly or the like.
In some configurations, the systems of the present invention are configured as in-line system that has a plurality of movable processing apparatuses. Advantageously, the in-line systems of the present invention allow for the processing of spools or rolls of a substrate, such as a thermoform, such that no manual handling of the thermoform is required in intermediate steps. The processing apparatuses can be configured to thermoform, pre-treat the substrate, metallize and/or cut the thermoform using the single in-line system.
The substrate may enter into the processing area either as a structural form which has been subject to prior processing (referred to as thermoforming) or the substrate may enter the processing area as a flat substrate and be subject to thermoforming followed by metallization, or alternatively vacuum metallization followed by thermoforming. For example, in some exemplary embodiments, the systems of the present invention include a series of movable processing apparatuses on one or both sides of the substrate. The assemblies can all be adapted to perform the same function (e.g. metallize) or each of the processing apparatuses can perform different functions (e.g., thermoform, metallize and cut). For example, for one exemplary in-line system, the substrate can be moved to a first processing apparatus for shaping (e.g., thermoforming) of the substrate. The shaped substrate can be then be moved to a second processing apparatus which can deposit a metal layer onto the shaped substrate (e.g., vacuum metallization). Finally, the shaped and metallized substrate can be transported to a third processing apparatus that can cut the shaped and metallized form out of the substrate. It should be appreciated that additional processing apparatuses can also be incorporated into the previous example, such as surface treatment apparatuses, heating apparatuses, or the like.
In some exemplary configurations, the processing apparatuses of the present invention can include one or more modular units for providing multiple interfaces for processing the substrate. Such processing apparatuses will be movable orthogonal to the plane of the substrate and rotatable so that a desired processing interface of the modular units can be moved into position to process the substrate. Such a configuration allows for a multitude of processes to be accomplished either on a single sheet of material or as a part of a continuous inline process in which a polymer or flexible film is unrolled and processed from beginning to end.
Typically, each processing apparatus includes at least three modular units, and preferably between three and six modular units. Each modular unit of each processing apparatus can have the same or different functions. For example, in some processing apparatuses each of the modular units will have the same modular unit, for example a metallization unit. The metallization unit will be used deposit a metal layer onto the substrate. Once the metal source has been depleted in the metallization unit, the processing apparatus can be rotated and a metallization unit having a full metal source can be used. Once the depleted metal source has been rotated away, the metal source can be manually or mechanically replaced. Such a configuration limits the xe2x80x9cdown timexe2x80x9d of the system and improves the output and production of the system.
Alternatively, each of the modular units of the processing apparatus can have a different functional modular unit. For example, a first modular unit can be used to heat the thermoform. The first modular unit can be rotated away and a second shaping modular unit can process and shape the substrate. Thereafter, the next modular units, such as a surface treatment assembly, metallization assembly, and cutting assembly modular unit can be rotated towards the substrate to process the substrate. Advantageously, if desired the rotatable, modular processing apparatuses allow for multiple or complete processing of the substrate while maintaining the position of a substrate in a single position. Such systems can reduce the footprint of the system on the manufacturing floor.
In exemplary embodiments, the present invention can create EMI/RFI shields that can be used within electronic devices and products to reduce the amount of electromagnetic radiation that is emitted from and enters the electronic device. In an exemplary embodiment, the EMI RFI shields enabled by the equipment described above are based upon the application of a relatively stable and uniform layer of aluminum on a polymer substrate. The present invention can apply any number of different metal layers (e.g., silver, copper, gold, nickel, or the like) to any number of substrate materials (e.g., polycarbonate, ABS, PVC, or the like) through a variety of metallization processes.
In one aspect, the present invention provides an apparatus for coating a substrate. The apparatus comprises a support that supports the substrate and at least one movable processing apparatus that can deposit a metal layer onto the substrate. The processing apparatus is movable between a first position adjacent the substrate and a second position apart from the substrate.
In another aspect, the present invention provides an apparatus for metallizing a substrate. The apparatus comprises a support that can maintain at least a portion of the substrate along a first plane and at least one rotatable processing apparatus that is movable substantially orthogonal to the orientation of the substrate. The processing apparatus comprises a plurality of modular units that includes at least one of a thermoform assembly, a heating assembly, a metallizing assembly, or a cutting assembly.
In another aspect, the present invention provides an in-line apparatus for creating an EMI shield, the apparatus comprises a conveyor assembly that moves a substrate from a first position to a second position and a movable shaping chamber disposed at the first position to shape the substrate. A metallization chamber can create a seal around the shaped substrate and can deposit a metal layer onto the shaped substrate, and a cutting assembly disposed at the second position to cut the shaped substrate, the cutting assembly being movable relative to the shaped substrate.
In yet another aspect, the present invention provides a method of manufacturing an EMI shield. The method comprises positioning a substrate on a support. A processing apparatus is moved adjacent to the substrate, a metal layer is deposited on the substrate and the processing apparatus is moved away from the substrate.
For a further understanding of the nature and advantages of the invention, reference should be made to the following description taken in conjunction with the accompanying drawings.